Summary: Three-dimensional study of cylindrical
morphology in a styrene-butadiene-styrene
block copolymer
Richard J. Spontak and Michael C. Williams
Center for Advanced Materials, Lawrence BerkeleyLaboratory, and Department of
Chemical Engineering, University of Ca/from/a, Berkeley, CA 94720-9989, USA
and David A. Agard
Department of Biochemistry and Biophysics, University of Cafiforn/a, San Francisco, CA
94143-0448, USA
(Received 6 July 1987;revised31 August 1987; accepted 7 September 1987)
When a block copolymer undergoes microphase separation, well ordered microstructures result which give
the copolymer unique thermal and mechanical properties. In relating these properties quantitatively to the
microstructure, and in devising models for the phase separation, theoreticians have always invoked highly
idealized structural elements. However, variations in the actual microstructure may also play a significant
role in these properties, so we describe here a method for highly detailed examination of these elements. By
using transmission electron microscopy (TEM), we have obtained projections ofa styrene-butadiene-styrene
(SBS)copolymer (30wt ~ostyrene) at tilt angles ranging from - 61.5° to + 48.5° in 5° increments. Applying a
filtered back-projection reconstruction method to this set of tilted projections yielded a three-dimensional
view of the polymer, revealing two different types of structures. The first type resembled cylinders in
hexagonal packing with some deviations from geometric ideality. In these cases, the microstructures were